This invention relates generally to anchors for lifting heavy loads and more particularly, to erection anchors of solid material that are embedded in a precast concrete member for both tension and shear load conditions.
The present invention relates to an erection anchor for lifting a concrete panel or structure by its edge, for example, in tilting a precast wall panel. Such a panel is often formed by pouring concrete into a form at floor level, either at, or remote from, a construction site. After the concrete has set or hardened, the horizontal panel is tilted or pivoted on one edge at one end by lifting an opposite end until the panel becomes vertical. Thereafter, the panel is positioned and can serve as a wall of a concrete building. The invention is, however, not limited to panel tilt-up operations. The system may be employed without modification in the lifting of a panel for transport or other purposes.
Heretofore, in the production of precast concrete members or panels that are to be handled by an edge-lifting operation, it is the practice to embed anchors of steel or iron in the precast concrete member. When lifting operations commence, the partially embedded anchor imposes substantial shear forces or stress into the concrete panel. To reduce the concentration of shear forces, it is known to attach a shear force resisting member or shear plate to the anchor body. A shear plate may be a length of right angle bar stock or a length of rectangular bar stock that is welded to the body of the erection anchor. With some known erection anchors, a shear plate is attached to only one side of the anchor body. Such an erection anchor must be oriented in the concrete panel such that the shear plate faces the direction of the lift force. In other words, in its horizontal orientation, the concrete panel has major upper and lower surfaces; and the erection anchor must be oriented such that the shear plate is between the erection anchor body and the upper major surface as well as substantially parallel to the upper major surface. Thus, as the concrete panel is lifted, the shear plate spreads the shear forces and permits the concrete panel to better react those forces.
The requirement to properly orient an erection anchor having a single shear plate is a further disadvantage. For example, if the anchor is misoriented by 180xc2x0 and the shear plate is located between the erection anchor body and the lower major surface of the concrete panel, the shear force resisting capability of the erection anchor may be lessened. Therefore, erection anchors having a welded shear plate impose a significant burden on the user to properly orient each of the erection anchors in a concrete form before the concrete panel is poured. Such a requirement substantially increases the time and cost associated with the manufacture of the concrete panel.
Other known erection anchors have shear plates welded to the anchor body. A disadvantage of known erection anchors with shear plates is that they are fabricated from multiple parts and thus, are expensive. The added cost of welding the shear plates to the anchor body is substantial compared to the cost of manufacturing the basic anchor to which the shear plate is being attached. Thus, the significantly greater manufacturing cost places a premium on the use of such erection anchors.
The head of the erection anchor is located in a recess in an end of the concrete panel. Often, the head is designed to receive a shackle lifting pin. With known erection anchors, the process of connecting the shackle, lifting the concrete panel and disconnecting the shackle, often results in the lifting shackle contacting and sometimes chipping the end of the concrete panel.
Therefore, there is a need for an erection anchor that is less expensive to manufacture, easier to use and less abusive of the end surface of the concrete panel.
The present invention provides an erection anchor that is more cost effective and does contact the end of the concrete panel with which it is used. The erection anchor of the present invention provides integral force bearing surfaces that help the erection anchor interlock with the concrete panel. Thus, the erection anchor of the present invention is not fabricated from multiple parts and is substantially less expensive to manufacture than known erection anchors. The erection anchor of the present invention has a head that is configured to receive and secure the shackle lifting apparatus so that it cannot contact an end of a concrete panel being lifted.
According to the principles of the present invention and in accordance with the described embodiments, the invention provides an erection anchor for use in a concrete panel having substantially parallel major surfaces and a recess in an end of the concrete panel. The erection anchor has a forged unitary body that includes a substantially cylindrical shank with one end embedable in the end of the concrete panel and an opposite end extendable into the recess in the end of the concrete panel. The forged unitary body also has a substantially cylindrical foot integrally formed with the one end of the shank with a diameter greater than a diameter of the cylindrical shaft. The forged unitary body is completed by a shackle-engageable, planar head integrally formed with the opposite end of the shank and disposable in the recess in the end of the concrete panel. The planar head has first and second opposed substantially planar surfaces and a boss integrally formed with the planar head and extending outward from the first planar surface. The boss forms a first plurality of bearing surfaces to interlock the planar head into the concrete panel, thereby increasing the strength of the interface between the erection anchor and the concrete panel.
In one aspect of this invention, the erection anchor has a second boss extending outward from the second planar surface along a length of the first lateral edge, and the first and second bosses form a second plurality of bearing surfaces that further interlock the planar head into the concrete panel. In another aspect of this invention, third and fourth bosses extend outward from the first and second planar surfaces, respectively, along a length of the second lateral edge. The third and fourth bosses form, respectively, third and fourth pluralities of bearing surfaces. The addition of more bosses on the planar head provides additional interlocking capability between the planar head and the concrete panel and, further increases the strength of the interface between the erection anchor and the concrete panel.
In another embodiment, the invention provides for an erection anchor to be used in a concrete panel that is lifted by a lifting device having a shackle. The erection anchor is formed by a forged unitary body having a substantially cylindrical shank with one end embedable in the end of the concrete panel and an opposite end extending into the recess in the end of the concrete panel. The forged unitary body further has a substantially cylindrical foot integrally formed with the one end of the shank and a shackle-engageable, planar head integrally formed with the opposite end of the shank. The planar head has an outer end with a cutout shaped to receive an end of the shackle and hold the shackle therein during a process of using the shackle to lift the concrete panel. Thus, the shackle does not contact the end of the concrete panel during the lifting process.